A comparative activity study of Eucalyptus globulus bark-derived biochar and activated carbon supported heterogeneous acid catalysts for biodiesel synthesis via esterification

Herein, comparative performance of sulfonated biochar and sulfonated activated carbon derived from Eucalyptus globulus bark (EGB) as solid acid catalysts for esterification of palmitic acid (PA) with CH 3 OH to produce biodiesel was investigated. The catalysts, which were synthesized through sulfonation of EGB-derived biochar and activated carbon with H 2 SO 4 , were thoroughly characterized by various techniques, including BET, XRD, CHNS, FTIR, NH 3 -TPD, SEM, TGA and acid density determination. While both sulfonated biochar (E-BC@SO 3 H) and sulfonated activated carbon (E-AC@SO 3 H) possessed high carbon content and amount of acid sites, E-AC@SO 3 H was found to have large surface area and porous structure as compared to E-BC@SO 3 H which made the former more sufficiently active in the esterification reaction than the latter. The E-BC@SO 3 H and E-AC@SO 3 H demonstrated excellent catalytic activities by respectively converting 94.7% and 98.37% of PA under optimal reaction condition of 60 ° C with CH 3 OH/PA molar ratio of 10:1 and 1.5 wt% catalyst loading during 3.0 h reaction duration. In addition, both E-BC@SO 3 H and E-AC@SO 3 H were regenerated and reused five times, with PA conversions of 80.92% and 87.75% for E-BC@SO 3 H and E-BC@SO 3 H, respectively at the 5th cycle, suggesting that the two catalysts were relatively stable and were promising for sustainable biodiesel production via esterification. • Sulfonated Eucalyptus biochar (E-BC@SO 3 H) and activated carbon (E-AC@SO 3 H) catalysts are used for esterification reaction. • E-AC@SO 3 H exhibited excellent performance compared to E-BC@SO 3 H. • Palmitic acid (PA) conversion of least 94 % was achieved at optimal conditions. • The catalysts were reused 5 times with PA conversion > 80 %.